In fabricating circuitized structures, such as printed circuit boards, electroless plating is often employed to plate metal, such as copper, to form circuitization onto dielectric surfaces. In forming such circuitization, the surface of a photoimaged dielectric which is present on substrate, which has through holes photoimaged in the dielectric, is blanket coated with seed. Next, a photoresist is blanket coated onto the seed layer and photoimaged in a pattern corresponding to the designed cicuitization pattern. The line channels are developed away, and the work-piece is immersed in a electroless plating bath so that copper is additively plated in the channels atop the exposed seed; copper is also plated into the through holes in the photoimageable dielectric at same time. The photoresist is then stripped, leaving circuitization atop the dielectric. The seed which does not have copper deposited thereon, is then removed. If desired, the copper is then further plated.
However, conventional electroless plating methods often suffer from excessive seed deposition; the presence of excessive seed on a circuit board leads to leakage shorts, poor adhesion of the photoresist onto seed due to uneven surface. Excess seed can also lead to unwanted metal plating in subsequent steps.
It would be desirable to have a method for depositing seed which does not result in excessive seed deposition.